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Food processing - restaurant operations - 2

There are many ways to classify food, but no matter what the classification is, the food we eat every day has the same origin and purpose, which is to sustain human life.

3. Quality and preservation

3.1. Food quality characteristics

For food, the system of product quality characteristics includes nutritional value, sensory value and hygiene.

Nutritional value:

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This is the most important characteristic of food quality. It indicates the ability to provide nutrients, assimilation and energy to the body.

Nutritional value depends on 3 factors:

Food processing - restaurant operations - 2

- Chemical composition: is a factor that determines the nutritional value of food. If food contains beneficial ingredients for the body such as protein, glucid, lipid, vitamin... it has 3 effects on the body as follows:

+ Provide heat

+Maintain growth and replenish cells

+ Regulates metabolism and protects body tissues

- Digestibility: is the ratio of food absorbed by the body compared to the amount of food entering the body. Thus, the digestibility of food characterizes the level of food use by the body:

Digestibility % = Amount of food absorbed by the body

Amount of food entering the body

𝑥 100

Digestibility depends on:

+ Type of food: if food contains a lot of carbohydrates such as glucose, fructose, it is easier to digest than sucrose, maltose, starch... Food containing a lot of simple proteins is easier to digest than complex proteins such as sugar water, eggs, milk, it is easier to digest than vegetables, meat, fish, peanuts, soybeans,...

+Status and preparation method: well-cooked, finely chopped food is easier to digest than large, rare-cooked food. When cooked, food with a delicious taste and attractive appearance will be better digested.

+ Physiological state of the eater: the same type of food will have a higher digestibility for young people and healthy people, and a lower digestibility for sick people and the elderly...

- Heat generation: is the amount of heat generated by 100g of product, calculated in Kcal

The human body needs heat to balance body temperature, maintain life and activities. That heat is provided by fat, carbohydrates, and proteins in food. 1g of carbohydrates provides 4.1 Kcal

1g of protein provides 4.1 Kcal 1g of lipid provides 9.3 Kcal

For example: fresh cow's milk has 3.9% P, 4.8% G, 4.4% L

Heat generation: = (3.9 x 4.1) + (4.8 x 4.1) + (4.4 x 9.3) = 76.59Kcal

Actual heat production = Theoretical heat production x Digestion

= 76.59 x 96%

The higher the calorific value, the higher the nutritional value.

Perceptual value

Sensory requirements such as color, taste, state, shape...

These requirements represent the composition of the product. If the sensory requirements change, the composition of the food also changes and therefore the quality of the food also changes.

For example, good quality fish sauce has a characteristic color (brown to straw yellow) and a characteristic aroma. If the fish sauce turns dark green and has a foul odor, it means that the composition of the fish sauce has changed (amino acids are broken down), and the quality of the fish sauce is poor and may be completely spoiled.

Non-toxicity

According to experts from the Food and Health Organization (FAO/WHO), "Food safety is the assurance that food does not harm the health and life of consumers; ensures that food is not spoiled, does not contain physical, chemical, biological agents, or impurities exceeding the permitted limits; is not the product of diseased animals or plants that can harm the health of consumers"

Food poisoning agents include biological agents, chemical agents and toxins present in food.

Biological agents that cause food poisoning include: bacteria, viruses, molds, and parasites.

- Bacteria are the most common cause of acute food poisoning. For example, Salmonella, Staphylococcus areus, Clostridium botulinum (botulism), and Escherichia coli causing diarrhea are common poisoning phenomena.

- Virus: Rotavirus causes diarrhea, the habit of eating undercooked mollusks such as oysters, mussels, and clams is the main cause of Rotavirus poisoning.

- Mold: growing in the food environment has the ability to produce dangerous mycotoxins, especially aflatoxin produced in corn, beans, especially peanuts, due to the fungi aspegillus flavus and a parasiticus, which can cause liver cancer.

- Parasites: such as amoeba, Entamoeba histolytical in food causes bloody stools. Most cases of worm infection are due to poor personal hygiene, undercooked food or raw vegetables that are not washed. For example, tapeworm larvae in beef, pork, rice, freshwater fish...

Chemical agents that cause food poisoning include pesticides, heavy metals: arsenic, mercury, lead... and some food additives such as auramin, scarlet red, sudan III, rhodamine.

Toxins present in food such as solanine found in potato sprouts, cyanogen glucoside found in cassava and some poisonous mushrooms.

The non-toxicity of food is expressed by food hygiene and safety standards. These standards stipulate that food products do not contain or contain at acceptable levels agents harmful to the health of users such as heavy metal salts, toxins, pathogenic microorganisms, and also regulate the use of colorants, aromas, flavoring agents, food shelf life, and toxicity.

Food hygiene standards are usually set by health authorities.

3.2. How to confirm food quality

The quality of food is determined by a system of sensory and physical-chemical indicators. Physical-chemical indicators. These indicators are determined by sensory methods and experimental methods.

Sensory method

Determining food quality by sensory organs (smell, touch, taste, sight, smell) is called sensory method.

By sensory methods, it is possible to determine food quality criteria such as: shape, color, surface state, smell, taste and hardness of food.

- Taste and smell are two important criteria of food.

The taste of food is determined by the tongue. To determine taste, people distinguish between four basic tastes: bitter, sour, salty, sweet. Taste determination is carried out at temperatures specified in the standard, otherwise it is carried out at temperatures of 15-220 o C. When the temperature increases from 10-20 o C, the sensitivity to taste doubles, but when the temperature increases

to 35-40 o C, at 50 o C it decreases sharply and then disappears completely. Sensitivity to salty taste is best at 18-20 o C and to bitter taste is at 10 o C. When testing taste, do not taste for too long in the mouth and the time should not exceed 1 minute.

The smell of food is determined by the nose. When determining the smell of food, people distinguish the inherent smell of food from foreign smells such as the burnt smell caused by spoiled fat, the foul smell caused by mold growth, and the putrid smell caused by protein decomposition. Good food has a characteristic smell, the smell of food changes due to changes in quality.

To perceive a smell, the nose must inhale at least 50cm3 of air containing the odorant.

Because the sense of smell is retained in the nose, when testing multiple samples, preliminary classification is required, and intermittent testing should be performed, and clean air should be breathed in between tests.

- Hearing and touch have very limited effects when it comes to sensory evaluation of food quality indicators.

Advantages and disadvantages: Fast results, mobile, simple and inexpensive. However, the main disadvantage is that the assessment results depend on the subjectivity, experience and skills of the examiner, so the results are not highly accurate.

Experimental method

Is a method of determining the composition, structure, properties, and quality of goods by machinery or chemicals (indicators of the nature of food).

- Experimental methods include:

+ Microbiological analysis method to determine mold, yeast, bacteria

bacteria

+ Chemical analysis method to determine toxins in food

poisoning consumers, chemical components of food.

+ Advantages and disadvantages: this method often gives objective and accurate results but is costly because it requires equipment, machinery or chemicals and after testing the sample is often completely or partially destroyed.

Basis for food quality testing

- Based on standard documents: TCVN, TCN, TC are the bases for checking the quality of goods. Compare with those standards to conclude about the quality of goods in a scientific and grounded manner, ensuring consistency in quality management.

- Based on the technical process. Each product has a technical production process, the quality inspector uses that as a basis to find out the reason why the product does not meet quality standards or is damaged.

- Based on economic contracts: in economic contracts there are contracts for the purchase and sale of goods.

- Based on product samples: to offer products to customers, businesses must use product samples to introduce and advertise the shipment.

- Based on current regulations on quality: In each period, the state may have new regulations on the issue of goods quality inspection, so it is necessary to base on current regulations on quality to inspect quality.

3.3. Factors affecting food quality Physical factors such as air, temperature, humidity and light

- Air in direct contact with food causes some components of the food to

Products such as fats, pigments, and vitamins are oxidized. Air oxygen promotes the activity of

the action of microorganisms and insects that destroy food.

- Food moisture

When storing foods that contain a lot of water, that water is easily lost; conversely, dry foods easily absorb moisture from the air.

- Air humidity

o Air always contains water vapor and the level of dryness and humidity of the air is characterized by relative humidity.

o Relative humidity of air is the ratio between absolute humidity and maximum humidity of air at the same temperature and expressed as %.

If the absolute humidity of the air is denoted by a (g/m 3 )

The maximum humidity of air is denoted by A (g/m 3 ) at the same temperature as a, then the relative humidity of air is φ = ! 100%

!

Relative humidity of the air will directly affect the quality of food during storage.

o When the relative humidity of the air is high, food will absorb moisture, the moisture content in the goods will increase, reducing the quality, creating favorable conditions for mold to grow (tea, tobacco get moldy, sugar leaks, rice flour gets moldy...)

o When the air humidity is low, the goods will release moisture, the humidity in the goods decreases, causing the quality of the goods to change: vegetables and fruits will dry out, green fruits will not ripen...

So for foods containing a lot of water such as vegetables, fruits, meat, fish need to be preserved in

high relative air humidity (80-90%) to avoid drying out.

Foods that contain little water such as sugar, rice, flour, wood ear mushrooms, shiitake mushrooms, etc. need to be stored in conditions of low relative humidity (70-75%).

- Air temperature

Air temperature increases or decreases affect the quality of food because the activity of chemical and biochemical processes and the growth of microorganisms depend on the temperature of the environment.

Temperature changes will lead to changes in relative humidity of the air, so the humidity of the food will also change and change the quality of the food.

Temperature also directly affects the change in state of food (solid, liquid), the absorption and release of water vapor and other gases.

Therefore, most foods need to be stored at low and relatively low temperatures.

- Light has the effect of promoting many processes that occur in food and causing food to spoil, such as rancid oil, cheese and sausages changing color and flavor.

Chemical processes

Chemical processes occur that change the quality of food such as oxidation of fats and fatty products, vitamin decomposition and some changes in canned foods such as color and flavor of food.

Biochemical processes

Can occur in food under the influence of enzymes available in food and enzymes secreted by microorganisms.

Under the influence of enzymes, food can undergo autolysis and respiration.

- Self-resolving:

Autolysis is the decomposition of food components under the action of enzymes present in cells, changing the taste and hardness of food.

o Protein breakdown: according to the following diagram under the influence of protease enzyme

Proteins ! peptones ! polypeptides ! amino acids ! ketoacids, amine compounds, NH 3 , CO 2 and foul-smelling substances (indon, skatone, mercaptan)

o Fat breakdown:

Under the action of lipase enzyme, fat is broken down into fatty acids and glycerol. If the decomposition process continues, the final products will be CO 2 and H 2 O.

Autolysis has a great influence on the quality of food such as the quality of cooked meat and fish, the ripeness of flour, the formation of aroma of beer, cigarettes, tea, etc.

- Respiration

Some foods such as vegetables, fruits, seeds, and eggs are living organisms and continue to respire during storage.

The nature of respiration is the process of oxidizing organic compounds (mainly carbohydrates) to provide heat for cell life.

There are two types of respiration:

o Aerobic respiration: occurs when there is enough oxygen in the air, organic matter is completely oxidized to the final products of carbon dioxide, water vapor and heat.

o Anaerobic respiration: occurs when there is a lack or absence of oxygen in the air, organic matter is not completely oxidized but forms intermediate products and releases less energy than aerobic respiration.

The intensity of respiration is expressed by the amount of carbon dioxide released from a unit of product in a unit of time during the respiration process. Factors affecting the intensity of respiration.

o Temperature: within a certain range, as temperature increases, respiratory intensity increases. Respiration intensity is strongest at 45-50 o C, at higher temperatures, respiratory intensity gradually decreases.

o The higher the product humidity, the stronger the respiration.

o Light: light stimulates the respiratory process.

The respiration process reduces the amount of nutrients; changes the composition of the air; increases the temperature and humidity of the environment; changes the taste of the product; if the alcohol content exceeds 0.3%, it causes the cells of vegetables and fruits to rot.

To limit the effects of respiration, the temperature and humidity of food can be lowered during storage.

- Germination:

Sprouting is characteristic of some foods such as vegetables, fruits, and seeds during storage.

For example, when potatoes sprout, the starch is lost and solanine accumulates, which is harmful to the body. Therefore, when processing potatoes, all sprouts must be removed. When seeds sprout, the starch loses its ability to gelatinize, and the processed product becomes tough, so it should be stored at low temperatures to limit germination.

Microbial processes

Microbial processes such as fermentation, putrefaction, and mold that occur in food during storage under the influence of microorganisms reduce quality and lead to complete food spoilage.

Microbial processes include:

- Fermentation

Fermentation is the anaerobic decomposition of carbohydrates under the influence of enzymes secreted by microorganisms. For example, alcoholic fermentation, lactic fermentation, butyric fermentation.

o Alcoholic fermentation often occurs in foods that contain a lot of carbohydrates and are moist. At that time, starch turns into sugar and then turns into alcohol under the influence of microorganisms, causing some grains and vegetables to spoil. The suitable temperature for fermentation is 30-35 o C

o Lactic fermentation produces lactic acid which commonly occurs in milk and dairy products: vegetables, bread, making these foods sour and possibly spoiled.

o Butyric fermentation produces butyric acid, which causes vegetables to rot, pickles to become rancid, butter, milk, cheese to become rancid, and canned foods to swell.

o Acetic fermentation occurs due to acetic bacteria on the surface of foods.

alcoholic drink

When preserving wine and beer, acetic fermentation will sour and reduce the quality of wine and beer. Therefore, during the preservation process, it is necessary to pay attention to fermentation to maintain food quality.

- Rotting

It is the process of deep decomposition of protein that creates toxic and unpleasant-smelling substances such as indon, scaton, mercaptan... Foods that often rot are foods that contain a lot of protein and water (such as meat, fish, eggs, milk) and will lose their food value and can no longer be used.

- Mold

Because the fungus that appears on the surface of food is often white, green, yellow, brown, or black, it reduces the quality of the food and creates favorable conditions for rotting bacteria to thrive, making the food unusable.

- Food spoilage by insects and rats

Such as destroying rice, flour, dried vegetables and fruits, causing loss of quantity and reducing the quality of food during storage.

- The impact of packaging and packaging materials

Packaging and packaging materials have the effect of preventing loss of quantity, maintaining quality, avoiding the effects of mechanical impacts, ensuring necessary hygiene conditions, facilitating transportation and storage. Each type of food needs to be contained in separate packaging. For grease, it must be stored in waterproof packaging, canned foods need to be sealed, vegetables and fruits during storage still undergo biochemical processes and need to be kept in ventilated packaging.

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